Site specific phosphorylation represents a major pathway through which signal transduction stimuli influence gene expression. Phosphorylation of critical sites can influence binding of transcription factors to specific regulatory elements, affect heterodimer formation between different members within broad families of transcription factors and influence the effect of transcription factor binding on gene expression. As a prototype system for the generation of phosphorylation site specific anti-bodies to key regulatory mammalian transcription factors we propose the development, in Phase 1, of affinity-purified rabbit polyclonal antibodies to peptides encompassing phosphorylated and non-phosphorylated c-jun p39 at serine residues 63,73 and 246. These will be assayed for ability to discriminate phosphorylated and non-phosphorylated forms of purified c-jun p.39. In parallel, agarose conjugated antibodies and consensus sequence oligonucleotides will be developed as solid phase reagents for enrichment of c-jun p39 form nuclear extracts to enhance analysis of its extent of phosphorylation. In Phase II and III, these studies will be extended to the development of c-jun p39 phosphorylation site specific monoclonal antibodies, analysis of phosphorylation sites on transcription factors which form heterodimeric complexes with jun, such as members of the CREB/AFT family, and the isolation of hybridoma clones producing monoclonal antibodies specific for the phosphorylated form of the dipeptide Ser-Pro.